#include <unistd.h>
#include <errno.h>
#include <sys/resource.h>
#include <limits.h>
#include "syscall.h"

int nice(int inc)
{
    int prio = inc;
    // Only query old priority if it can affect the result.
    // This also avoids issues with integer overflow.
    if (inc > -2*NZERO && inc < 2*NZERO)
        prio += getpriority(PRIO_PROCESS, 0);
    if (prio > NZERO-1) prio = NZERO-1;
    if (prio < -NZERO) prio = -NZERO;
    if (setpriority(PRIO_PROCESS, 0, prio)) {
        if (errno == EACCES)
            errno = EPERM;
        return -1;
    } else {
        return prio;
    }
}
